New to 1721 IOS (12.3)

[waifurchin]

Insanely basic question:

1721 router with WIC-1T in WIC0. Serial (v35) connected to an external CSU/DSU then via T-1 to the internet.

When applying config commands like "no ip mask-reply" to the serial interface, do I apply the command to interface Serial0, interface Serial0.1 or both to ensure it works properly?

Thanks

[ebreniz]

This is a interface configuration command, By default it is disabled means its no ip mask-reply by default. So If you apply this to a interface it will get applied to the whole sub-interfaces used below it . If you want to disable individually after applying to the physical interface you can give no ip mask-reply for that sub-interface only. You can check whether this is enabled or disable using "show ip interface command " Both for the physical interface and for the sub-interface.

by default you may see "ICMP mask replies are never sent"